【LeetCode 中等题 SQL】1-连续出现的数字

题目描述：编写一个 SQL 查询，查找所有至少连续出现三次的数字。

+----+-----+
| Id | Num |
+----+-----+
| 1  |  1  |
| 2  |  1  |
| 3  |  1  |
| 4  |  2  |
| 5  |  1  |
| 6  |  2  |
| 7  |  2  |
+----+-----+
           

例如，给定上面的 

Logs

 表， 

1

 是唯一连续出现至少三次的数字。

+-----------------+
| ConsecutiveNums |
+-----------------+
| 1               |
+-----------------+
           

解法1。3个表join，Id连续，Num相等，输出的字段distinct一下重命名就可以。

select distinct l1.Num as ConsecutiveNums from Logs l1
left join Logs l2 on l1.Id = l2.Id-1
left join Logs l3 on l1.Id = l3.Id-2
where l1.Num = l2.Num and l1.Num = l3.Num
           

解法2。和上面的解法一致，但没有用join，是默认join了吗？

select distinct l1.Num as ConsecutiveNums
from 
    Logs l1,
    Logs l2,
    Logs l3
where
    l1.Id = l2.Id - 1
    and l2.Id = l3.Id - 1
    and l1.Num = l2.Num
    and l2.Num = l3.Num